1. Technical Field
The present invention relates to a method for manufacturing a vibrator, a vibrator, and an oscillator.
2. Related Art
In recent years, piezoelectric vibrators have been developed that include a piezoelectric element having a piezoelectric layer sandwiched by top and bottom electrodes on a substrate. Such piezoelectric vibrators are used as, for example, oscillating portions (oscillator elements) of oscillators such as clock modules.
For example, JP-A-2007-267109 discloses the following steps: forming a piezoelectric element serving as a driving portion on an SOI (Silicon on Insulator) substrate; forming a plurality of beam portions (vibrating portions) and a gap portion in the silicon layer of the SOI substrate; removing the oxide layer of the SOI substrate via the gap portion; and forming an opening (recess portion) under the vibrating portions. JP-A-2007-267109 also discloses a support portion including a first support portion that is continuous to the silicon layer and a second support portion that is connected to the plurality of vibrating portions, the second support portion having a function of preventing vibrations of the plurality of vibrating portions from propagating to the first support portion. In order to have such a function, the length (the length in a direction parallel to the extending direction of the vibrating portions) of the support portion is an important factor in the design of piezoelectric vibrators.
However, in the technique disclosed in JP-A-2007-267109, because an SOI substrate is used, the cost is high. Furthermore, in the technique of JP-A-2007-267109, even if an inexpensive silicon substrate is used, in the technique of JP-A-2007-267109, etching performed to determine the depth of the recess portion and etching performed to determine the length of the support portion are performed in the same step, and it is therefore difficult to separately control the depth of the recess portion and the length of the support portion. For this reason, there are cases where it is not possible to form a highly accurate vibrator.